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A descriptive measure of a sample

statistic


method of organizing, summarizing, and presenting data

descriptive statistics


The group of all items of interest

population


the process of making an estimate. prediction, or decision about a population based on sample data

statistical inference


a set of data drawn from a population

sample


the data can be arranged in order & differences b/w data values are meaningful

interval scale


the data consists of names, labels, or categories. There are no criteria for ordering the data from smallest to largest

nominal scale


the data can be arranged in order & both & ratios b/w data values are meaningful. Also data has a true, absolute zero.

ratio scale


the data can be arranged in order. However, differences b/w data values either can;t be determined or are meaningless

ordinal scale


The Requirements of a Random Sample

1. Each indiv. in population of interest must have an equal probability of being of being included in the sample 2. They all have equal chance of being picked


Divide the entire population into preexisting segments or clusters. The clusters are often geographic. Make a random selection of clusters. Include every member of each selected cluster in the sample.

Cluster sampling


Create a sample by using data from population members that are readily available.

Convenience Sampling


A simple random sample of n measurements from a population is a subset of the population selected in a
manner such that every sample of size n from the population has an equal chance of being selected.

Simple Random Sampling


Divide the entire population into distinct subgroups called strata. The strata are based on a specific characteristic such as age, income, education level, and so on. All members of a stratum share the specific characteristic. Draw random samples from each stratum.

Stratified Sample


Number all members of the population sequentially. Then, from a starting point selected at random, include every kth member of the population in the sample.

Systematic sampling


A variable that describes an individual by placing the individual into a category or group, such as male or female.

Qualitative variable


A quantitative variable has a value or numerical measurement for which operations such as addition or averaging make sense.

Quantitative variable


numerical measure that describes an aspect of a population.

Parameter


Given a random sample of 9 skiers at Vail:18, 25, 32,16, 41, 52, 29, 58, 23Give the 5 number summary values w labelsX=

XMin= 16; Q1= 20.5; Med (Q2)= 29; Q3= 46.5; Xmax=58 Age of skiers


What is IQR and how do you find it?

Interquartile RangeQ3Q1= 20.5


How do you find the sample mean?

Summation of X divided by n


How do you find the median?

Order the data and then find the physical middle; Position= (n+1)/2


How do you find the mode?

it is the most frequent


How to find Weighted Mean

Summation (Weight x Data) / Summation(Weight)


How do you find the Range?

Xmax  Xmin


How do you find the sample mean?

Summation(X) / n


How do you find the sample standard deviation?

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Computational Formula (Standard Deviation)

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Population Standard Deviation

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Sample Variance

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Population Variance

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Sample Mean for Grouped Data

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